Heaven, for John Harbison, isn’t easy to get into. At any rate, not in his new Requiem, a BSO commission that had its world premiere last Thursday. It encompasses "eternity in an hour," and most of that shattering hour is spent by a chorus, four vocal soloists, and the orchestra yearning to untangle the knots of earthly suffering, guilt, and remorse; fearing judgment and praying — aching — for redemption and forgiveness. Passages of ecstatic joy are a mysterious mixture of beauty and terror (a sublime beauty almost more terrifying than the fear of damnation) — and those moments are hard-earned. There’s such amplitude, so much going on, it’s more than one can take in from a single hearing (I went back to hear it again). On opening night, the audience gave the piece, the performers, and the composer a prolonged standing ovation.

"A composer is someone who carries around a lot of impractical thoughts — sometimes over a long time frame," Harbison told musicologist John Daverio during their pre-concert discussion. His first inspirations for a Requiem came long before any commission. He composed the Introit back in 1985; the first notes appeared on the opposite side of the page on which he jotted down his first thoughts about The Great Gatsby. In 1991, he wrote a Sanctum and misfiled it, he said, so it stayed virtually lost for seven years. In 1995, Helmuth Rilling’s Stuttgart Bachakademie chose Harbison to contribute the Recordare to a 13-composer collective "Requiem of Reconciliation" honoring the victims of World War II (just as Verdi’s first work on his Requiem was a contribution to a collective "Requiem for Rossini" — probably the work that inspired Rilling, who made its first recording). The Metropolitan Opera commissioned The Great Gatsby in 1996. In 1999, Harbison composed a Hostias. The BSO commission, part of the centennial celebration of Symphony Hall (Catherine and Paul Buttenwieser are acknowledged for their generous support), came in September 2001. Three of its sections were in essence already written. The rest of the Requiem was composed after September 11. "The events of that fall made my purposes clearer," Harbison writes in the published score.

"Requiem æternam, dona eis, Domine" ("Lord, give them eternal rest"), the chorus begins softly, with the word "æternam" ominously repeated, a whispered echo reverberating over a restless sea of dark harmonies. The double prayer for mercy ("Kyrie eleison/Christe eleison") is represented in intense overlapping fugues. What else can one do except repeat and repeat the outcry? This entire Requiem, maybe more than any other, emphasizes supplication — in every form, from formal prayer to seductive flattery, from timid beseeching to outright demand.

Harbison follows the traditional Requiem order, first liturgy then poetry: the "Dies iræ" ("Day of wrath"), the mediæval Latin poem, in obsessive rhyming triplets, about the Day of Judgment. Leaping flames in the trumpets flicker over grim trombones. On the word for "trembling," a flexatone (the most unusual instrument in a spectacular array of percussion) gets a vigorous shaking; it sounds like a muffled fire alarm. People in the audience last weekend actually looked around in questioning dismay. In the "Tuba mirum" ("The trumpet, spreading its wondrous sound through the graves of the earth"), instead of the expected brassy blasts, Harbison gives us muted trumpets and trombones, sarcastic — and jazzy. Later, in the "Quid sum miser" ("What can I say, a poor wretch?"), bluesy woodwinds accompany the first fearful solo voice, in this case plangent mezzo-soprano Margaret Lattimore.

In this section and in the following Recordare, surrounded by delicate combinations of winds and chimes (bells jogging the memory?), the four soloists take center stage. Fearless soprano Christine Brewer delivered an imposing invocation to the "powerful king of majesty" ("rex tremendæ"), rising to a piercing plea for salvation, in vivid contrast to Lattimore’s quieter despair and warmer though still tentative hope. Tenor Paul Groves and bass-baritone Jonathan Lemalu began their own prayers for salvation, entering one at a time, then overlapping. In the quiet Lacrymosa, the low-string pizzicatos seem like falling tears while soloists and chorus sing together for the first time — joining public and private grief. The section ends with an exciting Amen fugue, almost a war cry, building inexorably to a sudden stop and followed by a hushed repetition of the prayer for eternal rest. Fade out. End of part one.

In the Offertorium (the offering of sacrificial prayer and praise), we turn back from poetry to ritual, with the piquant harmonies of late Stravinsky. The solo quartet here has the fastest and lightest music in the Requiem — like the quicksilver laughing fugue at the end of Verdi’s Falstaff ("All the world’s a joke"). And this leads into the ecstatic Sanctus — a combination of celebratory chiming (marimba, vibraphone, glockenspiel) and scary percussion (timpani, temple block, a brilliant drum "cadenza" by Frank Epstein) in exuberant but unsettling rhythm (7/8), extolling the overwhelming glory of God. Hosanna! Harbison takes us out of time and place by recalling the distant and the exotic: mediæval, Byzantine, even farther east to the land of the gamelan — some place where the hieratic is inseparable from the everyday.

Some of the most moving music is still to come, as the spiritual struggle begins to wind down. The entreaties are now purely for rest — eternal rest. In the Agnus Dei, a searching violin obbligato (concertmaster Malcolm Lowe) alternates with the soprano’s jagged and increasingly desperate invocation to the gentle Lamb of God (Brewer especially impressive here) and the chorus’s level intoning of its persistent prayer: grant us rest. In the "Lux æterna," a synæsthetic halo of light in the form of tolling bells surrounds the vocal quartet. Fear is still present in the "Libera me"; it’s the deepest voice — Lemalu’s — that "trembles," then stops suddenly and whispers, "et timeo" ("and I’m afraid"). The mezzo-soprano sings of the "bitterness" of that "day of disaster and misery" ("calamitatis et miseriæ"). Timpani taps are both solemn and unearthly.

But it’s still not over. Harbison adds a final section not included in most Requiems (though it’s in the most understated one, Fauré’s): "In Paradisum," which becomes a slowly syncopated pastoral lullaby for chorus and solo violin, almost a waltz — a shimmering, dancing ascent into a Heaven finally achieved.

The outstanding soloists, the orchestra (in top form — as it has not always been for new works), and John Oliver’s astounding Tanglewood Festival Chorus (singing this large-scale and complex new work from memory) all were in the unusually loving hands of Bernard Haitink, who was leading his first premiere of an American piece. As always, performers seem to want to please him — he knows how to make them sound good. But instead of his usual negligence, he seemed to be leading with conviction, clarity, and sympathy and allowing the piece a convincing shape and focus.

Harbison spoke about the standard text of the Requiem as an "accidental yet extremely durable assemblage" — one that gives composers a variety of opportunities — and a "chance to measure ourselves against the composers of the past." In this Requiem, the variety is there, certainly in the glittering array of orchestral color. Yet the tone is consistent — yearning, struggling, tragic. Even the most joyous music is permeated with foreboding, and that ties it to our own time. And as we know from the great Requiems of Verdi, Berlioz, and Fauré, these are the very pieces that last.

HAITINK WAS HAVING a good night in general. I’m seldom impressed with him as an interpreter, and I hadn’t thought much of his generalized note-by-note Mozart and Mahler the week before. Harbison’s Requiem was preceded by an unlikely choice: Beethoven’s sunny and charming (yet musically sophisticated) Symphony No. 4. What was the point? I wasn’t expecting much.

But Haitink captured the mysterious, exploratory tread of the slow introduction, then made the orchestra erupt into Beethoven’s ebullient and teasing Allegro vivace. A reed problem caused a sour oboe splat from the source I’d have least expected, but John Ferillo (obviously unhappy) recovered for the lovely Trio in the third-movement Scherzo. The "voice" of this symphony, though, is surely the clarinet, and William R. Hudgins had one of his best nights too.

What Haitink managed to do here that he hadn’t done the week before was maintain movement. In the slow movement, pulsing cellos, basses, and timpani kept the river flowing. That pulse would occasionally rise to the surface, then subside again into the undercurrent. The third movement was a jolly frolic; the finale was dynamic and buoyant. The orchestra maintained its articulation at increasing speeds and changing volumes (you could hear every note in the basses as they flew along). And the best joke was saved for last: the sudden foot on the brakes (over already?), then one last explosion of mirth — Beethoven’s "Gotcha!"

So what could have been better preparation for the tragic Requiem than a symphony of such comic spirit? Haitink obviously took pleasure in this contrast. And the Beethoven must be a piece he feels plugged into. I also suspect that the close work he must have put into the demanding new piece paid off in his handling of the old one.

SHAME ON ME! Two weeks ago I asked readers to guess the other Oscar-winning composers besides Tan Dun whose music the BSO has performed. I was thinking of André Previn and John Williams. But an attentive reader was shocked that I left out the most respected composer ever to win an Academy Award: Aaron Copland, who got an Oscar for his score to The Heiress (the movie version of Henry James’s Washington Square). There’s also Erich Wolfgang Korngold and more recently John Corigliano. And if you count special events at Tanglewood, the BSO has performed concert music by one Oscar-winning songwriter, Richard Rodgers. It has also played works by an Oscar nominee, George Gershwin, who never won — his great "They Can’t Take That Away from Me" lost to "Sweet Leilani." Shame on the Academy!

Now, when is the BSO going to play some Bernard Herrmann?